Salivary secretion induced from isolated, perfused rat submandibular glands by sympathomimetic agents

Saliva secretion was elicited from the isolated preparations by isoproterenol and phenylephrine, at concentrations from 10(-8) to 10(-5) M. The volumes of saliva secreted during a 60-min period, the rates of flow and the electrolyte composition of saliva secreted in response to each secretagogue were similar to those in vivo. Replacement of perfusate Na+ inhibited the secretion of fluid induced by isoproterenol (75 per cent) and by phenylephrine (99 per cent). It also reduced the Na+ and K+ concentrations of saliva elicited by the two secretagogues and inhibited isoproterenol-induced protein secretion (81 per cent). Omission of Ca2+ from the perfusate also inhibited fluid secretion (isoproterenol-stimulated, 84 per cent; phenylephrine-stimulated, 99 per cent) and isoproterenol-induced protein secretion (69 per cent). The absence of the divalent cation in the perfusate resulted in increased Na+ and decreased K+ concentrations in isoproterenol-stimulated saliva and in reduced K+ concentrations in phenylephrine-stimulated saliva. Administration of 10(-5) M phentolamine did not modify the volume of saliva secreted in response to isoproterenol, but reduced the response to phenylephrine by 90 per cent. The antagonist caused some reduction in the Na+ and K+ concentrations of isoproterenol-stimulated saliva, but did not modify those of phenylephrine-evoked secretion. Little recovery in fluid secretion was observed when the isolated gland was perfused with complete perfusate in the presence of phenylephrine after perfusion with Na+- or Ca2+-free solutions. Thus perfused rat submandibular glands are fully functional preparations, which respond to sympathomimetic agents of the alpha and beta types.(ABSTRACT TRUNCATED AT 250 WORDS)